Heat curable solventless liquid prepolymer

Abstract

A heat curable, solventless liquid prepolymer formed from an N-(R-oxymethyl) acrylamide; a rubber monomer such as isoprene, butadiene or alkyl esters of acrylic acid; and a nitrile monomer such as acrylonitrile or methacrylonitrile. The prepolymer is formed with sufficient chain transfer agent to establish a weight average molecular weight which is less than about 25,000. The prepolymer is heat curable to form a solid polymer with excellent compression set, tensile strength and fuel resistance. The method of formulating these polymers is also disclosed.

Having thus described and claimed my invention, I claim: 
     
       1. A liquid heat curable prepolymer substantially free from solvents which can be compounded and cured at about 360° F. to form a cured product having a compression set of about 20-30%, a Shore A hardness of about 70-89, tensile strength of about 410-780 psi, percent elongation of about 120 to about 140% and fuel resistance of about 49-62%, said prepolymer formed from the polymerization of at least about 65% of a free radical polymerizable rubber formable monomer selected from the group consisting essentially of conjugated dienes, alkyl esters of acrylic acid and alkyl esters of methacrylic acid;   and at least about 20% of a nitrile monomer selected from the group consisting of acrylonitrile and methacrylonitrile; and   at least about 4% of an acrylamide monomer having the following general formula ##STR5## wherein R 1  is selected from the group consisting of C 3  -C 22  alkyl, ether, aldehyde, ketone, amide, ester, imide and phthalimide   in the presence of an amount of chain transfer agent effective to establish the weight average molecular weight of said prepolymer at less than about 25,000.   
     
     
       2. The prepolymer claimed in claim 1 comprising about 65-75% of said rubber formable monomer, 20-30% of said nitrile monomer, and 4-10% of said acrylamide monomer. 
     
     
       3. The prepolymer claimed in claim 1 wherein said acrylamide monomer is N-(isobutoxymethyl)acrylamide. 
     
     
       4. The prepolymer claimed in claim 1 wherein R represents C 4  -C 8  alkyl. 
     
     
       5. The prepolymer claimed in claim 1 wherein said nitrile monomer is acrylonitrile. 
     
     
       6. The prepolymer claimed in claim 1 wherein said rubber formable monomer is selected from the group consisting of butadiene, isoprene, C 2  -C 10  alkyl esters of acrylic acid, and C 4  -C 8  alkyl esters of methacrylic acid. 
     
     
       7. The prepolymer claimed in claim 1 wherein said rubber formable monomer is isoprene. 
     
     
       8. The prepolymer claimed in claim 1 wherein said chain transfer agent is t-octyl mercaptan. 
     
     
       9. The prepolymer claimed in claim 1 wherein sufficient chain transfer agent is incorporated to establish the weight average molecular weight of said prepolymer in the range from about 10,000 to about 20,000. 
     
     
       10. A method of forming a liquid heat curable prepolymer which when compounded and cured at about 360° F. capable of forming a cured product having compression set of about 20 to about 30%, a Shore A hardness of about 70-89, a tensile strength of about 410 to about 780 psi, a percent elongation of about 120 to about 140, a fuel resistance of about 49-62%, a tensile elongation of about 140% comprising: mixing at least about 65% of a free radical polymerizable rubber formable monomer, selected from the group consisting essentially of conjugated diene, alkylesters of acrylic acid and alkylesters of methacrylic acids,   at least about 20% of a nitrile monomer selected from the group consisting of acrylonitrile and methacrylonitrile and at least 4% of an acrylamide having the following general formula ##STR6## wherein R 1  is selected from the group consisting of C 3  -C 22  alkyl, ether, aldehyde, ketone, amide, ester, imide, and phthalimide,   and polymerizing the above foregoing monomers in the presence of an effective amount of a chain transfer agent wherein the prepolymer formed has a weight average molecular weight less than about 25,000.